Process of preparing zinc and chlorine



Patented Dec. 21, 1943 PROCESS OF PREPARING ZINC AND CHLOR INE Ernst Kuss, Hans Holm, and Fritz Stietzel, Dnisburg. Germany; vested in the Alien Property Custodian No Draw g. Application December 16, 1938, Se-

rial No. 246,063. In Germany December 24,

4 Claims.

This invention relates to the manufacture of zinc and chlorine by lixiviating chlorinated roasted zinc sulfide-containing materials.

Zinc and chlorine have already been obtained from the solutions resulting from the lixiviation of chlorinated roasted zinc sulfide-containing materials when subjecting the solutions after an intense purification to an electrolysis while using diaphragms. This process has not found. any technical application for the following reasons:

The strongly electro-ne'gative character of the zinc causes many troubles'in the electrolysis, es-

pecially when impure solutions are used. I Especially the electrolysis of zinc chloride solutions suflers from these troubles having an impairing effect on theyield. In this case especially iron and dissolved chlorine have a detrimental eflect on the current yield. It has been tried to avoid these troubles by the use of'diaphragms, the use of which, however, is connected with some disadvantages.

In accordance with the present invention we have found that it is unnecessary to proceed as mentionedabovc, i. e. to completely purify the solutions and to use diaphragms if carrying out the electrolysis with a mercury cathode. According'to the invention zinc and chlorine are obtained from solutions, resulting from the lixiviation of chlorinated roasted zinc sulfide-contalning materials while'subJecting the solutions to the usual purification, by electrolyzing the zinc alkali metal chloride solution thus obtained while using a mercury cathode, by carrying away the chlorine evolved as gas and by separating the 'zinc from the amalgam produced.

As zinc sulfide-containing materials the cheap nine-containing roasted pyrites can be used,

which are obtainedin large amounts in the manufacture of sulfuric acid. It is also possible to use zinc blends which are preferably mixed with roasted pyrites or other materials poor in zinc, the decomposition under these conditions being more complete and less subjected to troubles.

This procedure also makes it possibleto work up complex zinc ores, for instance complex leadzinc ores, which generally are found connected with pyrites. The roasting process can be carried out in the usual manner. For the grade of purity of the solutions the required purity of the zinc obtained in the electrolysis is decisive, not

the consideration or the current-yields, since slight impurities hardly diminish the currentyields-in contradistinction to the working with solid cathodes. For instance, when electrolyzing I solution with about 30 mm. Fe, 30 mars. Co

antimony, etc., are precipitated by means of lime while oxidizing at the same time by means of chlorine at a pH beneath '6. As a result of this purification there are obtained zinc chloride solutions, containing alkali metal chloride'as'well as magnesium-' and calcium-chloride. They are well suited for the electrolysis. The electrolysis by means of mercury cathodes can be carried out in the apparatus generally used in the industry. It is possible to workat room as well as as high temperatures. It is advisable to'proceed in that way that the amalgam thus obtained remains liquid. The mercury is led in the same direction together with the solution throughathe cells. The zinc amalgam can be worked up electrolytically as well as'thermally; it is advantageous to dissociate it by stages. The dissociation can take place in vacuo. The apparatus may work continuously or discontinuously. The mercury may be led in a closed circuit. Advantageously the amalgam is worked up continuously.

' While in the course of the known processes the exchange of the cathodes and the removing of examples Example 1 Roasted pyrites of 57.10% Fe, 1.99% Cu, 2.39% Zn, 240 ems/ton C0, 300 gms./ton Mn, 0.04% Sb.

3.45% S,0.11% As, 1.40% Pb, 4.05% S102, 82.0

gms/ton Ag, 1.02 gms/tonAu are after addition of 10% of sodium chloride, chlorinatingly roasted and lixiviated to produce a solution. This solution is decoppered by means of scrap iron and cooled to 0 C, to eflect the removal of the bulk of.

cells used in alkali metal chloride electrolysis, at

a temperature of 70 C. and a current density of 1200 amp/m. The electrolyte leaves the cells with a content of about 20 grams of zinc per liter. This zinc is precipitated with lime and the zinc hydroxide obtained is utilized in lieu oi the calcium compound for the purification of the initial solution. The obtained chlorine gas is purified in the usual manner, dried and condensed. There 'is obtained an amalgam containing 4.5% 01' zinc, from which the mercury is distilled ed. The zinc obtained is drawn of! into casting molds; it has a purity of 99.95%.

Example 2 f Roasted Meggen pyrites are mixed with copper containing roasted pyrites in a proportion of 1:1. The mixture contains 53.00% Fe, 0.55% Cu, 5.20% Zn, 240 gms./ton Co, 750 gms./ton Mn, 0.04% Sb, 0.14% As, 0.53% Pb, 8.30% SiOr, 3.95% 8, 25.00 gms./ton Ag, 0.82 gms./ton Au. Sodium chloride in an amount of 12% is added to themixture and according to the method of Example 1 a zinc solution containing 65 grams of zinc per liter is obtained This solution is electrolyzed at a temperature of about 75 C. with a current density 01 800 amperes per square meterwhile using amalgam cathodes. An amalgam containing 5% of zinc is produced in the electrolysis. Further treatment is effected in the manner described above.

We claim:

l. The process of preparing zinc and chlorine 2. A process as in claim I in which the mercury as well as the solution are passed through the cell in the same direction.

3. A process as in claim 1 in which about mgrs. iron, 20 mgrs. cobalt and 10' mgrs. nickel to 100 gms. zinc are present in the incompletely purified solution.

4. The process of preparing 'zincand chlorine cium-chlorides as well as iron, cobalt and nickel to an extent whereby it is too impure to work up electrolytically with solid cathodes, and subjecting the said solution to electrolysis in 9. diaphragm-less cell with a liquid mercury cathode,

recovering the chlorine as gas and separating the zinc from the mercury-zinc amalgam.

' ERNST KUSS.

HANS HOHN. FRITZ S'HE'IZEL. 

